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Tool-first calculator

BTU calculator: cooling, heating, and mini-split.

Estimate the BTU load for central cooling, whole-home heating, or a single-room mini-split. Rule-of-thumb math tuned to climate and envelope. Real equipment sizing needs a Manual J on your actual home; this gets you close enough to sanity-check what a contractor proposes.

Independent FatBook v3 cost indexVerified permit/source data where availableReviewed by Leonard "Chuck" Thompson
sq ft
Whole-home modes assume typical window count and occupancy for the area. Exposure applies to the mini-split mode only.
Cooling load
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Local installed cost

What an installer charges for your scope.

The numbers above are material counts and sizing. Below shows what a contractor typically charges in your city for an installed version of this scope, scaled from FatBook's cost index of BLS wages + Craftsman labor hours + permits + materials.

Pick the cost-index service that matches the scope you're scaling. The default is the trade's headline service.
National Average · Central Air Conditioning Installation
$9,728
Range $9,039 to $11,130 · lowest realistic price $9,039
How to use this result
  • Cooling mode sizes an AC or heat pump in tons. Heating mode sizes furnace output BTU/hr. Mini-split mode snaps a single room to the nearest standard head size.
  • Oversizing is the most common and most expensive mistake in residential HVAC. A unit more than half a ton above the load short-cycles, dehumidifies poorly, and wears out sooner.
  • Heating equipment is sold by output BTU/hr. A furnace listed at 80,000 BTU input with 96% AFUE delivers about 76,800 output. Compare loads against output, not the number on the box.
Cost-index version: 2026-07-23. Read the FatBook methodology, or use the bid and true cost calculators for an installed bid check.
Data Sources Used On This Page
  • Independent FatBook v3 cost index for btu calculator.
  • BLS OEWS wage inputs (https://www.bls.gov/oes/) and FRED PPI material inflation (https://fred.stlouisfed.org/) references.
  • Craftsman labor-hour references and contractor overhead benchmarks.
  • Permit assumptions are included only where verified permit/source data is available.
Cost-index version: 2026-07-23
Updated: Jul 2026
Sources: BLS, ACCA, Craftsman, FRED
Reviewed by: Leonard "Chuck" Thompson
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Cost index built by David Olson, Creator of the Cost Index & Permit Dataset · Methodology reviewed by Leonard "Chuck" Thompson, LC Thompson Construction Co., Owner (retired) · 2026-07-23